Results

Three ALV-J strains associated with hemangioma were isolated and their proviral genomic
sequences were determined. The three isolates, JL093-1, SD09DP03 and HLJ09MDJ-1, were
7,670, 7,670, and 7,633 nt in length. Their gag and pol genes were well conserved,
with identities of 94.5-98.6% and 97.1-99.5%, respectively, with other ALV-J strains
at the amino acid level (aa), while the env genes of the three isolates shared a higher
aa identity with the env genes of other hemangioma strains than with those of ML strains.
Interestingly, two novel 19-bp insertions in the U3 region in the LTR and 5' UTR,
most likely derived from other retroviruses, were found in all the three isolates,
thereby separately introducing one E2BP binding site in the U3 region in the LTR and
RNA polymerase II transcription factor IIB and core promoter motif ten elements in
the 5' UTR. Meanwhile, two binding sites in the U3 LTRs of the three isolates for
NFAP-1 and AIB REP1 were lost, and a 1-base deletion in the E element of the 3' UTR
of JL093-1 and SD09DP03 introduced a binding site for c-Ets-1. In addition to the
changes listed above, the rTM of the 3' UTR was deleted in each of the three isolates.

Conclusion

Our study is the first to discovery the coexistence of two novel insertions in the
U3 region in the LTR and the 5' UTR of ALV-J associated with hemangioma symptoms,
and the transcriptional regulatory elements introduced should be taken into consideration
in the occurrence of hemangioma.